In a small bowl, dissolve the cornstarch in the water.
In a medium saucepan, combine the berries with the orange juice, sugar and salt and bring to a simmer over moderate heat, stirring until the sugar dissolves. Cook for 5 minutes, stirring occasionally. Stir in the dissolved cornstarch and simmer until the liquid is slightly thickened, about 30 seconds.
Using an immersion blender, gently blend until a thick sauce forms. Serve chilled.